Triangle ABC AD-bisector angle C = 30 degrees angle BAD = 69 degrees Find: angle ADB.

By property, the bisector AD in triangle ABC has divided <A into two equal angles: <BAD and <DAC. It is known that <BAD = 69 °. Then we define what is equal to <A:

69 ° + 69 ° = 138 °.

In a triangle, the sum of all angles is 180 °. Find out the degree measure <B:

180 ° – 138 ° – 30 ° = 12 °.

Applying the same rule about the sum of all angles of a triangle, we calculate the unknown degree measure <ADB:

180 ° – 69 ° – 12 ° = 99 °.